Root canal treatment is a tooth-saving treatment that eliminates infections, protects the decontaminated tooth from future infections, and—if needed—restores the tooth at crown level either with or without use of a post. During this treatment the root canals, which mainly contain the nerve tissue and blood vessels are cleaned, shaped, decontaminated and subsequently filled with an inert filling such as gutta percha. In cases where the remaining tooth structure is insufficient to support a proper reconstruction of the dental crown, a metal or glass fiber post is positioned in one of the root canals and a core build-up is created in order to support and provide retention for the prosthetic restoration (i.e. crown).
Root canal treatment can fail or lead to complications due to several reasons, e.g. insufficient cleaning of the root canals, incomplete filling of the root canals, untreated canals since these were missed by the practitioner, root perforations or file fracture during shaping of the canals, root fractures . . . .
According to literature the use of 3D tooth assessment can reduce the risk of complications during root canal treatment. Cone beam computed tomography (CBCT) for instance can be used in the management of endodontic problems, i.e. in the assessment of the true size, extent, nature and position of peri-apical and resorptive lesions, in the assessment of root canal anatomy, root fractures, and the nature of the alveolar bone topography around teeth, or in the planning of endodontic surgery (cf. New dimensions in endodontic imaging: Part 2. Cone beam computed tomography. International Endodontic Journal, 42, 463-75, 2009). Cone beam computed tomography provides more comprehensive diagnostic data compared to intra-oral radiography, hence resulting in more accurate diagnosis and monitoring, and therefore improving the management of endodontic problems.
Micro-computed tomography (μCT) has been used in academic settings, on extracted teeth for three-dimensional reconstruction and assessment of tooth and root canal morphology for endodontic research purposes (cf. An application framework of three-dimensional reconstruction and measurement for endodontic research, Yuan Gao, Ove A. Peters, Hongkun Wu, Xuedong Zhou, J Endod 2009; 35:269-274). The internal and external anatomies of the tooth were reconstructed and the dimensions of root canal and radicular dentin quantified. The root canal dimensions were calculated by first defining the root canal middle line and then calculating the distance from the middle line to the root canal surface. These distances were subsequently visualized by means of a colour-code on the root canal surface. The minimal distance from the external root surface to the root canal surface was also calculated and visualized by means of a colour-code. Then the evaluation of the root canal preparation was performed by registering pre- and post-preparation images of the tooth. In both image sets the root canal was segmented and visualized in 3D for a graphic comparison of the change of canal shape, namely the amount of dentin removal during canal preparation. In addition the perforation risk during removal of a broken instrument could be analysed. After virtually simulating the removal of the said broken instrument by means of a user specified trepan/trephine on the computer, a thickness analysis on the remaining root was performed, as a means to quantify the risk of root perforation.
UK patent application, 1108002, Method and system for establishing the shape of the occlusal access cavity in endodontic treatment, describes the use of a three-dimensional computer model of the tooth including the pulp chamber and the root canals in order to define the optimal shape and geometry of the occlusal access cavity to the tooth roots prior to root canal treatment.
While the use of 3D computer images and models has been reported for the preparation of root canal treatment, the available prior art fails to provide a method that is usable in the daily clinical practice. Current CBCT technology does not provide the required image resolution to allow for planning of the root canal treatment, since the root canals are often hardly if at all distinguishable from noise in the images. Even in cases where the root canals can be discerned, the reliability of measurements performed on the images, e.g. with respect to the canal dimensions, is insufficient to provide added value when planning the clinical intervention. In addition, radiation doses required for CBCT imaging can drastically exceed those of traditional X-rays, potentially adding risk to the patient, and making the technique currently unsuited for most endodontic indications. μCT imaging is even less suitable: currently, there is no commercially available equipment for acquiring μCT images on patients, since fields of view are too limited, required radiation doses too high and data acquisition times too long with this technology. μCT imaging currently only works on extracted teeth, in specific set-ups for research purposes.